Characterizing Spherical, Aspherical, Free-form Lenses

For the functionality of optical systems, the geometrical shape of the functional optical surfaces and their position relative to each other is a decisive criterium. However, small-aperture polymer optics, which are in great demand, for example in mobile phone cameras, endoscopes, or car sensors, cannot yet be checked with sufficient accuracy using standard metrological methods. At the Laser World of Photonics trade fair in Munich, the Fraunhofer Institute for Production Technology IPT from Aachen, Germany, presented a new tomographic method that can measure such optical components with a small aperture non-destructively and in one step.

OCT scanning head with lens tray for shape and centering measurement of injection-molded micro lenses (Source: Fh. IPT)

The new method is based on optical coherence tomography and can capture both functional surfaces of an optical system simultaneously in one single scan. In this way, not only the surfaces can be characterized, but also the alignment of the functional surfaces to each other can be checked. The process is also capable of characterizing spherical and aspherical lenses as well as free-form surfaces.

During the exhibition, the IPT researchers demonstrated their OCT-based inspection system for geometrically complex polymer micro-optics at the Fraunhofer booth. The new measurement system offers manufacturers of sensor technology and imaging systems an efficient and cost-effective way of quality assurance: Since the system can determine the shape and centering of both functional surfaces in just one single step, it delivers a result in shortest time that cannot until now be achieved so quickly and accurately with any conventional optical measurement method. The IPT is now planning to fully automate the tomographic process so that in-line integration into existing optical production lines will become possible. (Source: Fh. IPT)

Link: Tomographic optical testing (M. Riediger), Production quality and metrology, Fraunhofer Institute for Production Technology IPT, Aachen, Germany

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